Presidential campaigns used to begin about a year before the election.
For instance, John F. Kennedy formally announced for President at the beginning of January 1960.
But with the development of primaries and some caucuses over time, it has become customary that once the midterm elections take place, that early in the third year of the Presidential term, we see candidates announcing for President.
But it is now indicated that Donald Trump may announce as early as this month, July 2022, four months before the Midterm Elections of 2022.
Supposedly, he is trying to divert attention from the January 6 House Committee, and the testimony of Cassidy Hutchinson, which makes clear that Trump was engaged in treason and sedition on January 6, 2021, when the US Capitol was attacked.
The potential exists for up to 25 Republicans becoming candidates for the White House.
And if Joe Biden chooses not to run, or even if he does, there is also the potential for an equal 25 Democrats to engage in the Presidential campaign, although the number proabably would be lower than the number of Republicans.